After purchasing the transfer case and transmission, the next area of concern was the driveline geometry. I soon realized that my offset rear differential on the Spicer 53 may pose a problem with my centrally located output shaft on the NP 205. Even though the drive-shaft would remain rather long, I did not want to risk the chance of having U-joint explosions. So I came to the conclusion that a center set rear differential was needed. I consulted my useful Willys America repower guide and found that a Ford 9" is a good swapping candidate because of the 5.5" 5lug bolt pattern. Off to the wrecking yards I went. After about 10min of searching I found a 1980 Ford F-150 with a 31 spline Ford 9" that matched the width of my Spicer 53 almost perfectly. It had a lousy gear ratio, 2.50:1, but for $110 I couldn't pass it up. Another bonus with the Ford 9" is the self-adjusting 11" drum brakes. Ahhhh, stopping power!

At this point I realized that the gear ratio I choose for my axles would be very much influenced by the tire size I select. The spring over conversion provided far more lift than I had expected. I put a 33" tire on the truck just for comparison and found 33s would look too small. Essentially, I had so much clearance between the tires and the fenders that 33s looked (for lack of a better word) goofy. I set my limit at 35" and decided that the 3.54:1 gear ratio that came with the Dana 44 front end would suffice. Now I just needed to get a set of matching gears for the rear. As is turns out, the only gear ratio that I could get for the 9" that even came close to the 3.54:1 ratio D-44 was 3.50:1. I bought a used set of gears from West Coast Differentials for about $200 with an install kit.

With all these gear ratios in mind, I decided to do a little comparison between the gear ratios of a stock Willys truck and what I have now. I found that the overall gear ratio for my rig when original was 33.59:1. With my current drive train configuration I have 45.58:1. At first glance this looks pretty good, however, the oversized tires must be taken into consideration. Guessing that stock 7.00X16 tires have an outside diameter of 30", I figured that I would need a 17% increase over the stock overall gear ratio to match the crawling speed of an original Willys PU. Well 33.59 + 17% gives a ratio of 39.30:1. Wow, I am still ahead on crawl ratio. Keep in mind that my attitude towards swapping out original parts has changed drastically since I started this project, but I am still elated that my final crawl ratio rivals that of a stock rig.